At present, a double-sided light box has found an increasing application. A LED module is increasingly applied to the light box. In actual application, the LED module is arranged on the frame of the double-sided light box. Such a LED module is generally equipped with a LED lens with ellipsoidal intensity distribution to allow the LED module to generate a viewing angle of 10×50 to 60°. In this way, light from the LED module can be projected from sides onto two light box screens of the double-sided light box. However, this type of lens fails to project all the light onto the light box screen, that is to say, a part of the light is projected onto the frame opposite to the LED module. In addition, the intensity distribution of the light projected by such a LED lens onto the light box screen is not uniform.